Self-powered and washable wearable displays

A textile-based wearable display module technology that is washable and does not require an external power source has been developed by a research team from KAIST.

To reduce the problems associated with using external power sources, while enhancing the practicability of wearable displays, Professor Kyung Cheol Choi from the School of Electrical Engineering and his team fabricated display modules on real textiles that integrated polymer solar cells (PSCs) with organic light emitting diodes (OLEDs).

PSCs have proved a promising candidate for a next-generation power source, especially for wearable and optoelectronic applications because they can provide stable power without an external power source, while OLEDs can be driven with milliwatts. However, they are vulnerable to external moisture and oxygen, so an encapsulation barrier is essential if they are to function reliably.

The conventional encapsulation barrier is sufficient in normal environments; however, it loses its characteristics in aqueous environments, such as water so limiting its commercialisation as part of a wearable display.

The team looked to address this problem by employing a washable encapsulation barrier that can protect the device without losing its characteristics after washing through the use of atomic layer deposition (ALD) and spin coating. By using this encapsulation technology, the team was able to confirm that textile-based

wearing display modules including PSCs, OLEDs, and the proposed encapsulation barrier exhibited little change in characteristics even after 20 washings with 10-minute cycles. Moreover, the encapsulated device operated stably with a low curvature radius of 3mm and boasted high reliability.

Finally, it exhibited no deterioration in properties over 30 days even after being subjected to both bending stress and washing. Since it uses a less stressful textile, compared to conventional wearable electronic devices that use traditional plastic substrates, the researchers believe this technology could accelerate the commercialisation of wearing electronic devices. Importantly, this wearable electronic device in daily life can save energy through a self-powered system.

Professor Choi said, “I could say that this research realised a truly washable wearable electronic module in the sense that it uses daily wearable textiles instead of the plastic used in conventional wearable electronic devices. Saving energy with PSCs, it can be self-powered, using nature-friendly solar energy, and washed. I believe that it has paved the way for a ‘true-meaning wearable display’ that can be formed on textile, beyond the attachable form of wearable technology.”